Submitted to: Journal of Applied & Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 22, 1995
Publication Date: N/A
Interpretive Summary: Spiroplasmas are a unique group of bacteria that are closely associated with a wide variety of insects. Since many of these insects are classified as crop and livestock pests, it has been proposed that spiroplasmas that are genetically engineered to produce insect lethal toxins may be used as insect biocontrol agents. Toward this goal, several spiroplasmas from insect pests are being characterized and their relationship to previously characterized spiroplasmas is being determined. In this study, several isolates from flies and beetles were shown to be closely related. The results indicate that the spiroplasma classification system may need to be re-evaluated prior to giving specific spiroplasmas binomial (latin) names. Clearly, a classification system and the inter-relatedness of various spiroplasmas from insect pests needs to be understood prior to an effective implementation of these microorganisms as biocontrol agents. The information obtained from this study will help scientists interested in determing microbial biodiversity by providing a classification criteria for the characterization of spiroplasma isolates. In the case of insect biocontrol potential, the information from this study will allow the identification of spiroplasma strains associated with insect pests that can be used in the development of genetically engineered spiroplasmas as insect biocontrol agents.
Spiroplasma group XIV strain EC-1, isolated from the gut of a lampyrid beetle Ellychnia corrusca, was previously determined to be serologically indistinguishable, by spiroplasma deformation test, from several spiroplasmas from tabanid flies (including strains TC-1 and TS-1). Criteria for erecting a new species which includes all three strains have therefore been met. It was hypothesized that similarities among these strains reflect transmission among lampyrid beetles, in which the organisms could overwinter, and tabanid adults in which lateral transmission could occur in spring, summer and fall. This conjecture was investigated by RFLP analysis. Although spiroplasma strains EC-1 from E. corrusca, TC-1 from Tabanus calens, and several strains from T. sulcifrons could by distinquished genotypically by this technique, there was considerable similarity among the profiles. Similarly, serological profiles among lampyrid and tabanid spiroplasmas varied more widely in their profiles than would be expected if the isolates reflect a single biovar, supporting the possibility of lampyrid-tabanid transmission cycles, as well as yet to be discovered host relationships. Genotypic (RFLP) analysis may therefore be a companion to serology in elucidating spiroplasma diversity, and may provide clues to strain host range.